Support system for cryogenic liquid storage tank



Dec. 31, 1963 1. L. WISSMILLER 3,115,983

SUPPORT SYSTEM FOR CRYOGENIC LIQUID STORAGE TANK Filed Dec. '7, 1959 2Sheets-Sheet 1 INVENTOR. Ivan L. Wissmil/er Merriam, Smith 8 Marshall AT TOR/VE Y5 Dec. 31, 1963 1. WISSMILLER ,1

SUPPORT SYSTEM FOR CRYOGENIC LIQUID STORAGE TANK Filed Dec. 7, 1959 2Sheets-Sheet 2 INVENTOR. Ivan L. Wissmi/ler Merriam, Smith 8 Marshall AT T OR/VE Y8 United States Patent 3,115,983 7 SUPPORT SYSTEM FORCRYOGENIC LIQUID STGRAGE TANK Ivan L. Wissmiller, Chicago,'lll.,assignor to Chicago Bridge & Iron Company, Chicago, 111., a corporationof Illinois i I Filed Dec. 7, 1959, Ser. No. 857,664 11 Claims. (Cl.220-) This invention relates to a multi-walled tank for the storage ofliquefied, normally gaseous materials. It particularly relates to animproved supporting system for the inner vessel or vessels of amulti-wall storage tank employed especially as a low temperature storagefacility.

In designing a mu-lti-wall tank for the storage of liquefied, normallygaseous materials or so called cryogenic liquids one of the problemsthat confronts the designer has to do with the properties of thematerials which must be used in the vessel which contains the cryogenicliquid. Carbon steels are to be avoided in those portions of the tankwhere low temperatures are encountered. Carbon steels can be employed inservices where temperatures of above F. occur but at lower temperaturesit is not advisable to use such steels. This permits the use of carbonsteels in the Outer shell construction; however, different materials ofconstruction must be used for fabricating the vessels exposed to theextremely low temperatures which do not become embrittled at lowtemperatures. The use of a variety of construction materials complicatesthe design of support structures for suspending the inner vessels withinthe outer vessels in spaced relationship each to the other. For example,in a cryogenic storage tank for extremely low temperature service, suchas for liquid oxygen service, one of the most usual and mostsatisfactory materials for the construction of the inner storage vesselis aluminum. It is quite difiicult, and sometimes impossible, to weldaluminum to other more conventional materials. As a consequence one ofthe most effective means for connecting components of the tank togethercannot be used. Moreover, differences in coefiicients of thermalexpansion make it diflicult to provide bolted mechanical connections.

In addition, it is desirable to limit the possible paths of heattransfer into the inner vessel by making the support structures for theinner vessel as small and as light as practicable. Various suspensionmeans such as chains, straps, or other supporting devices have beenemployed in multi-wall tank construction to minimize any temperaturegradient from the inner storage vessels to the outside atmosphere.Factors which afiect the rate of heat transfer through the supportstructure include the length of the metallic path between the ambienttemperature at the outer vessel wall and the point of connection of thesupporting structure to the inner vessel, the cross sectional area ofthe support, and the coefiicient of thermal conductivity of the supportstructure.

According to the present invention there is provided a support means forsuspending the inner storage vessel or vessels within the outer shell ofa multi-wall type storage tank especially adapted for the storage ofcryogenic liquids, which comprises a system of tension bars, cables orthe like extending from the inner vessel to points of attachment at orabout the outer shell. The tension members are attached to the innervessel so as effectively to eliminate any substantial bending momentwhich otherwise might be induced and also to eliminate the necessity forwelding or bolting [the tension support members to the inner vessel.

FIGURE 1 is an elevation view of a multi-wall spherical cryogenic tankwith the outer vessel wall partially cut away;

FIGURE 2 is afragmentary enlarged view taken in the plane 22 of FIGURE1;

FIGURE 3 is an enlarged partial sectional view of an alternativeembodiment showing adjustable connecting means for the support system;

FIGURE 4 is a View taken in the plane 44 of FIG- URE 3;

FIGURE 5 is a view of another alternative embodiment of securing thesupport to inner shell connection; and

FIGURE 6 is a cross-sectional side view along line 66 of the embodimentshown in FIGURE 5.

In the specific embodiment illustrated in FIGURE 1 there is shown amulti-wall tank having an outer spherical shell 10 supported by aplurality of columns 11 extending from a suitable foundation 12 topoints of attachment about the equator of the outer vessel It}. Acircular reinforcing memberp13 encircles the outer vessel It) at thelevel of the connections of the support structure hereinafter described,which in this case is at the equator, to provide a stiffening of theouter shell in the area of such attachment. A plurality of support basemembers 14 for attachment of the several vessel supports, forconvenience referred to as gusset plates, is attached to the reinforcingmember 13 by Welding or other means. Support base members 14 are spacedaround the reinforcing member 13 in pairs as shown in FIGURE 2. Theterminal ends of a tension bar or cable 15 employed in holding the innervessel 16 in substantially rigid, spaced relationship within the outershell 10 are attached by suitable means respectively to the two supportbase members 14 which comprise a pair. The tension member 15 is bentaround a semicircular pad plate 17 suitably attached as by welding tothe wall of inner spherical vessel 16. Retaining lugs 18 employed toretain the tension bar or cable 15 on the peripheral face of pad plate17 are attached to pad 17 by suitable means, such as by bolts, screws orwelding. if deemed desirable or necessary, stiffening bars 19 can beattached to the wall of vessel 16 and the pad 17 to provide additionalstiffness and shear strength for transferring the loads from the vessel16 to the pad 17 for transmittal to the tension bars or cables 15.Suitable piping for filling, emptying and venting; manholes and otherconventional tank fittings normally used are not shown for simplicity.

The construction is shown in greater detail in FIGURE 2, in which thevarious parts have been assigned the same reference numerals as inFIGURE 1.

In the embodiment shown in FIGURES 1 and 2, the semi-circular pad 17 isconstructed of the same material as is used for the inner vessel 16, ora similar material which can be readily secured by welding to the wallof inner vessel 16 and which Will have substantially the samecoefiicient of expansion as the material employed in the construction ofthe inner vessel 16 in order that the two parts may readily be attachedtogether by welding and further that they will have the same coefficientof thermal expansion, thus minimizing shear stresses occurring acrossthe joints upon diiferential cooling or heating of the parts. Similarly,the stifiening bars 19 are made of the same material. The tension member15, on the other hand, can be of a dissimilar material having eithergreater strength or a lower coeflicient of thermal conductivity than thematerial of which the inner vessel 16 and pad 17 are made. Since thetension member 15 is not integrally attached to any portion of the innervessel 16 or the pad 17, no welding or thermal problems arise. Thetension member 15 is merely bent about the curved portion of pad 17 andheld in place by lugs *18, remaining free to adjust to differentials inthermal movement or to strain caused by tensioning.

It is obvious that variations in this arrangement can be made withoutdeparture from the source of this invention. For example in place oflugs 13 as shown in FIGURES l and 2 a flange which could be an integralpart of the pad 17 or a separate part suitably attached to pad 17 willserve the same purpose. In addition, while the two ends of the tensionmember are shown as converging toward each other, they may as well beparallel or divergent. Either converging or diverging ends are preferredin order to afford a greater degree of lateral stability to the supportof the inner vessel. Similarly, while pairs of support base members 14are shown, it is obvious that a single support base member of suitabledimensions can be utilized.

The tension member 15 shown in FIGURES 1 and 2 can consist of a suitablyshaped rigid bar, or flexible support such as a chain or wire rope orcable of high strength material having ductility at the low operatingservice temperature. The material of construction employed forfabricating the tension member preferably should have a lowercoefficient of thermal conductivity than the wall of the inner storagevessel. If a rigid bar is used it is preferably secured to the supportbase members 14 by Welding. Such a construction, however, does notpermit subsequent adjustment of the support structure which may bedesired. Moreover, it is impracticable to use this type of connectionwhere a high strength flexible chain or cable is employed instead of atension bar. Generally 3 to 8 tension members can be used to support theinner storage vessel. Additional supports can be used if needed.

FIGURES 3 and 4 show a different embodiment of a portion of theinvention in which a high strength cable having the requisite lowtemperature characteristics is used as the tension member 15. In thisillustrative embodiment a wire rope bridge socket is interposed betweenthe support base pad eye 31 and the flexible tension member 15 such as awire rope or cable or chain. The socket has threaded ends 32 which areengageable by nuts 33 to position collar 34 thus affording anadjustability not inherent in the construction shown in FIGURES l and 2.Duplicate systems can be used for securing each terminal end of theflexible tension member or only one end can be made adjustable. One ofthe advantages of using wire rope or cable is that the wire, being colddrawn, is of higher strength than a hot rolled bar of the same material.In addition, the twisted strands of wire rope afford a longer and moretortuous heat transfer path than an equivalent length of bar material ofthe same cross sectional area and therefore has a lower coeflicient ofthermal conductivity.

The selection of the size and shape of the pad 17 depends upon suchfactors as the amount of shear to be transmitted through the attachmentbetween the pad and the inner vessel 16, the stiffness of the innervessel 16 and the bending moment resulting from the eccentricity ofloading caused by the fact that the axis of the tension member 15 isspaced a slight distance outwardly from the neutral axis of the materialfrom which vessel 16 is constructed. While a semi-circular shape for thepad 17 is shown, any pad having a smoothly curved edge in contact withthe tension member 15 may also be effectively utilized. In selecting theshape of the pad it is desirable to eliminate points of local stressconcentration and a generally curved pad is therefore preferred whilesharp corners are to be avoided.

The pad is located on the wall of the inner vessel substantially at thepoint of tangency with the longitudinal axis of the tension member.Accordingly the position will depend upon the location of the supportbase member. It is preferred that the support base members be locatedadjacent the horizontal equator of the outer vessel; however, they canbe installed in other angularly displaced positions relative to thehorizontal equator.

It is obvious that the method of connecting the tension member 15 to theinner vessel 16 by means of the pad 17 results in a greatly reducedbending moment when compared with conventional methods of attachment andin particular when compared with conventional methods of attachment ofdissimilar materials which are not capable of being welded together.

Where there are likely to be significant dimensional changes in thetension member 15, or where it is anticipated that substantialadjustments may be necessary from time to time in the total length ofthe tension member 15, an alternate means for securing a flexibletension member 15 to the inner vessel 16 can be used as is shown inFIGURES 5 and 6. In this construction the tension member passes around asheave, that is attached to the support pad 17 welded to the wall of theinner vessel 16 to minimize the effect of frictional forces resistingdesired movement in the tension member 15. Pad 50 comprises a baseplatemember 51 welded to the wall of vessel 16. An upright leg 52 is fastenedto plate 51 and is provided with an opening 53 through which one end oflink 54 is connected. The other end of link 54- connects with the eye 55of pulley block 56 which has a sheave 57 around which is passed flexibletension member 15.

In constructing a cryogenic storage tank, materials are selected for theinner vessel and for that portion of the inner vessel support which willhave to operate at low service temperatures which do not becomeembrittled at the service temperatures. The outer shell on the otherhand, and its support structure need not be made of the more expensivelow temperature service material because they will operate atapproximately ambient temperature and a mild carbon steel is thereforesuitable. Materials which are suitable for the inner vessel and supportstructure include aluminum, stainless steel of the 300 series, andcertain nickel steel alloys such as Il /2% nickel, and 9% nickel.

The storage tanks of this invention are useful as low temperaturestorage facilities having capacities of 500 to 25,000 barrels; however,they can be used for storage in capacities outside this range. Thestorage vessels can be designed to withstand superatmospheric pressure,although this is not necessary if the temperature of the storedcryogenic liquid is at or about its boiling point. The space between theouter shell and the inner storage vessel can be insulated by anysuitable means, as, for example, by placing therein granular fibrous orsolid insulation, by evacuation of substantially all air from thisspace, or by a combination of these.

In the foregoing description reference has been made to a rnultiwalltank and an outer shell, and it should be understood that, since theouter wall or shell is designed primarily to act as a vapor barrier toprevent the accumulation and condensation of water vapor in theinsulating space, the outer wall or shell need be of substantialindependent strength. For example, if a rigid type of insulationmaterial is employed in the insulation space the outer vessel wall mayconsist merely of a layer of vapor impervious material, such as a metalsheet or foil, attached to the outer surface of the insulating material.By employing this type of construction it is necessary to provide anelevated structure to which the support base members can be secured. Asuitable structure could consist of horizontally placed, circular orpolygonal reinforcing member positioned in an elevated position by aplurality of peripherally spaced columns. The support base members couldbe secured to the reinforcing ring and the inner vessel supportedtherefrom employing the suspension system of this invention.

The foregoing detailed description and illustrative examples have beengiven for the purpose of explaining the invention and no unduelimitations in the claims which follow should be implied there-from.

What is claimed is:

l. A support system for a cryogenic liquid storage tank comprising anelevated structure spaced apart from the cryogenic liquid storagevessel, said structure having sufficient strength to support the weightof said vessel and its contents, suspension members attached to saidstructure and depending generally downwardly and inwardly therefrom andsecured to said vessel to support it in an elevated position, andrelatively thin pad plate members shaped to conform to the shape of aportion of the surface of said vessel and secured to the exteriorsurface of said vessel below the horizontal equator of said vessel to bein substantially surface to surface contact therewith, each of saidsuspension members comprising an open-loop metallic tension memberhaving its terminal ends secured to said structure, the bight of saidloop engaging said relatively thin pad plate member at a pointsubstantially tangential to said storage vessel.

2. A support system in accordance with claim 1 in which said pad platemembers are fabricated from the same material of construction asutilized in the construction of said vessel.

3. A support system in accordance with claim 1 in which tension membershave a lower coefiicient of thermal conductivity than the wall of thecryogenic liquid containing vessel.

4. A support system for a cryogenic liquid storage vessel comprising anelevated structure spaced apart from the cryogenic liquid storagevessel, said structure having sufiicient strength to support the weightof said vessel and its contents, suspension members attached to saidstructure and depending generally downwardly and inwardly therefrom andsecured to said vessel to support it in an elevated position, andrelatively thin pad plate members shaped to conform to the shape of aportion of the surface of said vessel and secured to the exteriorsurface of said vessel below the horizontal equator of said vessel to bein substantially surface to surface contact therewith, each of saidsuspension members comprising an openloop metallic tension member havingits terminal ends secured to said structure, the bight of said loopengaging said relatively thin pad plate member at a point substantiallytangential to said storage vessel, the bight of said loop beingcontiguous to said storage vessel.

5. A support system for a cryogenic liquid storage vessel comprising anelevated structure spaced apart from the cryogenic liquid storagevessel, said structure having sufiicient strength to support the weightof said vessel and its contents, suspension members attached to saidstru ture and depending generally downwardly and inwardly therefrom andsecured to said vessel to support it in an elevated position, andrelatively thin pad plate members shaped to conform to the shape of aportion of the surface of said vessel and secured to the exteriorsurface of said vessel below the horizontal equator of said vessel to bein substantially surface to surface contact therewith, each of saidsuspension members comprising an openloop metallic tension memberextending tangentially from said storage vessel and having its terminalends secured to said structure, said pad plate lying in peripheral,frictional engagement in the bight of said loop and having a lug forretaining the tension members in position whereby the weight of saidvessel and its contents is trwsmitted through said pad members to saidtension members.

6. A support system for a cryogenic liquid storage vessel comprising anelevated structure spaced apart from the cryogenic liquid storagevessel, said structure having sufficient strength to support the weightof said vessel and its contents, suspension members attached to saidstructure and depending generally downwardly and inwardly therefrom andsecured to said vessel to support it in an elevated position, andrelatively thin pad plate members shaped to conform to the shape of aportion of the surface of said vessel and secured to the exteriorsurface of said vessel below the horizontal equator of said vessel to bein substantially surface to surface contact therewith, each of saidsuspension members comprising a flexible, metal multi-wire cable,open-loop tension member having its terminal ends secured to saidstructure, the bight of said loop engaging said relatively thin padplate member at a point substantially tangential to said storage vessel.

7. A support structure in accordance with claim 6 in which at least oneof the terminal ends of said tension members is adjustably secured tosaid structure.

8. A support system for a cryogenic liquid storage tank comprising anouter shell, a plurality of tubular columns secured to the wall of saidshell and supporting said outer shell, an inner storage vessel suspendedwithin said shell and insulated therefrom, suspension members attachedto said outer shell and depending generally downwardly and inwardlytherefrom and secured to said vessel to support it in spacedrelationship within said shell, and relatively thin pad plate membersshaped to conform to the shape of a portion of the surface of saidvessel and secured to the exterior surface of said vessel below thehorizontal equator of said vessel to be in substantially surface tosurface contact therewith, each of said suspension members comprising anopen-loop metallic tension member having its terminal ends secured tosaid shell, the bight of said loop engaging said relatively thin padplate member at a point substantially tangential to said storage vessel,the bight of said loop being contiguous to said storage vessel.

9. A support system for a cryogenic liquid storage tank comprising anouter shell, a plurality of tubular columns secured to the Wall of saidshell and supporting said outer shell, an inner storage vessel suspendedwithin said shell and insulated therefrom, a compression ring membercircumscribing said outer shell and integrated with the wall of saidshell and the tubular supports therefor, suspension members attached tosaid shell and said ring and depending generally downwardly and inwardlytherefrom and secured to said vessel to support it in spacedrelationship within said shell, and relatively thin pad plate membersshaped to conform to the shape of a portion of the surface of saidvessel and secured to the exterior surface of said vessel below thehorizontal equator of said vessel to be in substantially surface tosurface contact therewith, each of said suspension members comprising anopen-loop metallic tension member having its terminal ends secured tosaid shell and said ring, the bight of said loop engaging the undersideof said relatively thin pad plate member at a point substantiallytangential to said storage vessel, the bight of said loop beingcontiguous to said storage vessel.

10. A support system for a cryogenic liquid storage tank comprising aspherical outer shell, tubular supports secured to the wall of saidshell about its periphery and supporting said shell, a spherical, innerstorage vessel suspended within said shell and insulated therefrom, acompression ring member circumscribing said outer shell and integratedwith the wall of said shell and the tubular supports therefor,suspension members attached to said shell and said ring and dependinggenerally downwardly and inwardly therefrom and secured to said vesselto support it in a suspended relationship within said shell, andrelatively thin pad plate members shaped to conform to the shape of aportion of the surface of said vessel and secured to the exteriorsurface of said vessel below the horizontal equator of said vessel to bein substantially surface to surface contact therewith, each of saidsuspension members comprising an open-loop metallic tension memberhaving its terminal ends secured to said shell and said ring, the bightof said loop engaging said relatively thin pad plate member at a pointsubstantially tangential to said storage vessel, the bight of said loopbeing contiguous to said storage vessel.

11. A support system for a cryogenic liquid storage tank comprising anelevated structure spaced apart from the cryogenic liquid storagevessel, said structure having sufficient strength to support the weightof said vessel (I and its contents, suspension members attached to saidstructure and depending generally downwardly and inwardly therefrom andsecured to said vessel to support it in an elevated position, relativelythin pad plate members shaped to conform to the shape of a portion ofthe surface of said vessel and secured to the exterior surface of saidvessel below the horizontal equator of said vessel to be insubstantially surface to surface contact therewith, each of saidsuspension members cornprising an open-loop metallic tension memberhaving its terminal ends secured to said structure, the bight of saidloop engaging said relatively thin pad plate member at a pointsubstantially tangential to said storage vessel, and means for retainingthe bight 0f the loop in engagement with said relatively thin pad platemember.

References Cited in the file of this patent UNITED STATES PATENTS883,479 Place Mar. 31, 1908 2,842,427 Kinzel May 26, 1936 2,924,351 Hawket a1. Feb. 9, 1960

1. A SUPPORT SYSTEM FOR A CRYOGENIC LIQUID STORAGE TANK COMPRISING ANELEVATED STRUCTURE SPACED APART FROM THE CRYOGENIC LIQUID STORAGEVESSEL, SAID STRUCTURE HAVING SUFFICIENT STRENGTH TO SUPPORT THE WEIGHTOF SAID VESSEL AND ITS CONTENTS, SUSPENSION MEMBERS ATTACHED TO SAIDSTRUCTURE AND DEPENDING GENERALLY DOWNWARDLY AND INWARDLY THEREFROM ANDSECURED TO SAID VESSEL TO SUPPORT IT IN AN ELEVATED POSITION, ANDRELATIVELY THIN PAD PLATE MEMBERS SHAPED TO CONFORM TO THE SHAPE OF APORTION OF THE SURFACE OF SAID VESSEL AND SECURED TO THE EXTERIORSURFACE OF SAID VESSEL BELOW THE HORIZONTAL EQUATOR OF SAID VESSEL TO BEIN SUBSTANTIALLY SURFACE TO SURFACE CONTACT THEREWITH, EACH OF SAIDSUSPENSION MEMBERS COMPRISING AN OPEN-LOOP METALLIC TENSION MEMBERHAVING ITS TERMINAL ENDS SECURED TO SAID STRUCTURE, THE BIGHT OF SAIDLOOP ENGAGING SAID RELATIVELY THIN PAD PLATE MEMBER AT A POINTSUBSTANTIALLY TANGENTIAL TO SAID STORAGE VESSEL.